Patent document 1 describes a fuel battery that includes a solid polymer electrolyte membrane and electrode catalyst layers arranged on both surfaces of the electrolyte membrane. A gas diffusion layer is laminated on an outer side of each electrode catalyst layer to form a membrane electrode assembly. A gas passage forming body is arranged between the membrane electrode assembly and a separator. Water guide passages are arranged between the gas passage forming body and the separator. Water is generated by an electrode reaction at the membrane electrode assembly and drained into the water guide passages through communication passages extending between the gas passages and the water guide passages.
When the above fuel battery is operated under a condition in which a large amount of water is generated by the electrode reaction, such as a high load condition or a high moisture condition, the water guide passages cannot sufficiently drain the water. Thus, the generated water overflows into the gas passages from the water guide passages through the communication passages and blocks the gas passages. This impedes gas diffusion and lowers the battery performance of the fuel battery.
Patent document 2 describes a fuel battery including a plurality of groove-shaped gas passages. End portions of the gas passages are arranged in a staggered layout. This increases the size (surface area) of water droplets generated at the end portions of the gas passages compared to when there is only one gas passage. Thus, the generated water may be forced out of the passages with a smaller gas pressure. This improves water drainage.
Patent document 3 describes a fuel battery including gas passages that are wider at a downstream side so that the passage cross-sectional area of each gas passage increases toward the downstream side. This limits blocking resulting from the generated water and improves water drainage.